Wood chip cutting machine

ABSTRACT

A wood chip cutting machine comprises a casing with a drum shaped cutter cage therein, the cage having a plurality of inwardly pointing cutters spaced around it. Cooperating with the cage is a rotor having arms each of which carries a thin doubleedged blade. Each blade is replaceable, and is clamped on its rotor arm by a retaining strip held in place by bolts. The blade protrusion is only about equal to the blade thickness, which is preferably 2 mm.

[ July 31, 1973 United States Patent [1 1 Maier WOOD CHIP CUTTINGMACHINE [76] Inventor:

3,297,262 1/1967 Skardal 241/90 Primary ExaminerGranville Y. Custer, Jr.Attorney-Leonard H. King [22] Filed:

ABSTRACT [30} Foreign Application Priority Data A wood chip cuttingmachine comprises a casing with m a drum shaped cutter cage therein, thecage having a plurality of inwardly pointing cutters spaced around it.

B02 18 14 Cooperating with the cage is a rotor having arms each 241 86of which carries a thin double-edged blade. Each blade is replaceable,and is clamped on its rotor arm by a re- [51] Int. Cl... [58] Field ofSearch taining strip held in place by bolts. The blade protrusion isonly about equal to the blade thickness, which is preferably 2 mm.

[56] References Clted UNITED STATES PATENTS 2.874.909 2/1959 Pallmann241/93 X 7 Clalms, 5 Drawlng Flgures PATENIE JUL3 1 I975 sum 1 OF 2 Invan for Gerhard Maier W000 CHIP CUTTING MACHINE The invention relates toa rotary chip cutting machine for producing wood chips, having chipcutter blades which cooperate with cutters forming a cutter cage.

BACKGROUND OF THE INVENTION In chip cutting machines the blades aresubjected to extreme wear and tear. To obtain a satisfactory cut and afavourable service life of the cutting edges of the blades, these aremade of high quality and hence costly material, and are securedinterchangeably to a base by means of countersunk screws. The blades aremade relatively thick to enable such screw fastening to be effective.The disadvantage of this prior art embodiment is that because of thequantity of high quality material used, the production of a rotor for arotary chip cutting machine is costly.

A further disadvantage is that since the cutting edges become blunt dueto excess wear, the chipping quality diminishes over a period of time.

It is an object of the invention to provide an improved rotary chipcutting machine, more especially the chipping blades of which are ofsimple structure require only a small quantity of high quality material,and substantially ensure the production of chips of uniform size.Moreover the cutting blades of this invention have a long service life,are positioned reliably and are easily interchanged.

According to the present invention there is provided a chip cuttingmachine for producing wood chips including a drum-shaped cutter cagefixed ina housing and provided on its circumference with cutter ribs inspaced relationship to one another, a plurality of cutters securedthereto by fixing means, a chip cutting rotor rotating in said cuttercage and connected to a driving device, said rotor being provided withrotor arms having chip cutting blades co-operating with the cutters ofthe cutter cage, each blade being clamped between a supporting surfaceof a rotor arm and a detachable fixing strip by securing means therefor,said blades being of a thickness between 1 and mm, and having twocutting edges so as to be reversible.

In a preferred embodiment each chipping cutter is formed as a thincutter blade having a thickness of between 1 and 5 mm, preferably 2mm,.and is. provided with opposing cutting edges; when one cutting edgehas worn out, the blade can be turned through 180 to use the secondcutting edge.

This thin cutter is a cheap discardable item and can be made with orwithout any cutting edge armour; the embodiment without armour and hencethe cheapest is preferred. 1

The individual cutters are clamped with the exceptionof a cutting edgeprojection corresponding to the cutter. thickness, between a rotor armand a retaining ledge. The retaining ledge, cutter and rotor arm aresecured by fixing screws passed therethrough. The fixing screws can beformed with surfaces acting directly on the blades.

At a cross-sectional corner remote from the cutter a retaining ledge ischamfered and/or radiused, so that when a cutter is located within thecutter cage, 8. receiving space is formed between the retaining ledgeand cutter cage. to reduce the cut material to small pieces.

To enable a chipping cutter with a worn'cutting edge to be turned, eachcutter has a retaining strip with its longitudinal edges recessed, witha cutter projection opposite the cutting edge, so that only the nuts ofthe fixing bolts need be removed, the assembly unit (cutter, retainingstrip and fixing bolts) being drawn off the rotor arm, turned through l,and fixed anew to the rotor arm.

Since each cutter is relatively thin, the construction in accordancewith the invention uses only a small quantity of high quality materialand is thus extremely economical.

On account of their projection beyond the holder to a distancecorresponding to the cutter thickness, the individual blades can wearonly up to the holder and then can be reversed or interchanged in goodtime, so that the deterioration of chip quality occurring in hithertoknown designs due to excessive cutting edge wear are substantiallyeliminated.

The invention will be described further, by way of example, withreference to the accompanying drawings, in which:

FIG. I is a perpendicular longitudinal section through a rotary chipcutting machine having a cutter cage fixed in a casing, and a chipcutting rotor cooperating with it;

FIG. 2 is a cross-section through the cutting means of chip cuttingrotor and the cutter cage surrounding it;

FIG. 3 is a cross-section on an enlarged scale through the cutting meansof the chip cutting rotor;

FIG. 4 is a front elevation of a chip cutter as used on the rotor,showing the retaining ledges in chain dotted lines; and

FIG. 5 is a schematic drawing showing the relative orientation of theblades.

A chip cutting machine in accordance with the invention for producingwood chips has a housing 25 in which a drum-shaped cutter cage 10 ismounted: this cutter cage 10 is provided on its circumference withspaced fixing ribs 26, to which two cutters are detachably mounted withcutting edges facingin opposite directions (located at an angle to oneanother), i.e'. cutting blade 14 and a stock blade 15 are detachablymounted. The stock blade 15 is retained interchangeably by fasteningbolts 27, and the cutting blade 14 by a retaining strip 28 held againstthe cutting blade 14, and secured by bolts 29 to the cutter cage rib 26.An adjustable chip passage gap 30 is formed between the leading cuttingblade 14 in the direction of rotation of the rotor, and the adjacentcutter cage rib 26' holding the rear stock cutter 15 through which gapthechips produced arrive in the chip space 32.-

A chip cutting rotor 11 mounted rotatably in the housing 25 extendswithin the cutter cage 10 and'is provided with rotor arms 11 formingbeating vanes, each carrying chip cutting blades 13 having cutting edgesI 13a, 13b; each blade is detachably mounted on each rotor arm 12 andco-operates with the cutters 14,15 of the cutter cage 10. The chipcutting rotor 13 is driven by a shaft 31 which is either directlyconnected to a driving device (not shown) such as a motor, or indirectlyvia gear means such as a belt pulley and belt.

The housing 25 forms a chip space around the cutter cage 10 from whichspace there is at least one chip removing opening on the underside.

The housing 25 is closed at the end face opposite the driving side, by acover 34 mounted detachably on the housing 25, through which opening thecutter cage can be removed from the housing 25 for replacing its cutters14, 15.

The cutter cage 10 is of frusto-conical shape tapering towards the cover34, and the rotor is also frustoconical. The rotor driving shaft 13 issubstantially horizontal.

The cutter cage ribs 26 are provided with a coating 35 such as animpact-resistant armoured coating at their inside surface between thetwo cutters 14, 15, facing the rotor 12. The housing 25 in the upperregion opposite the cover 34 has a timber inserting opening 36.

Each blade 13 co-operating with the cutting blades 14 and the stockblades 15 is supported against the wall of its rotor arm 12 leading inthe direction of rotation of the chip cutting rotor, by means ofcentering belts or centering projections, and is fixed laterally andvertically and clamped by means of a retaining strip 16 detachablymounted on the rotor arm 12.

Each blade 13 is located with its cutting edge within the rotationaljacket of the rotor 11 and thus extends diagonally to the rotationalaxis of the rotor 11; this cutter position is established by rotor arms12 extending diagonally to the axis of rotation of the rotor.

The rotor arm 12 for the blade mounting, provided with an impactresistant armour coating 17 on its end, has a space 18 located in thefrontal corner region in the direction of rotation, and also a pluralityof bores 19, passing through the wall thickness.

For mounting purposes each blade 13 has at least one retaining strip 16associated therewith which is at least partly accommodated in the space18 and by means of which it is detachably secured by fixing screws 20passing through the blade 13 and rotor arm 12, with nuts 21 screwed onthe free ends thereof.

Each blade 13 is provided with fixing holes 22 for its positionallocation. These fixing holes 22 register with screw holes 23 in theretaining strips 16, so that the same fasteners are used for theretaining strip 16, exerting a clamping action, against the blade 13.

For centering the blades 13 the fixing screws 20 are provided at thehead end with a cylindrical portion 20a, which are a close fit in theblade fixing holes 22.

The blade 13 is between 1 and 5 mm thick, prefera bly 2 mm, and has twoopposed cutting edges 13a, 13b so that it is reversible. The blade 13has a uniform cross-section over most of its length, but tapers towardsits two end faces.

The retaining strips 16 have a shape similar to the shape of the blades,but are slightly smaller, so that in the region of at least one lateraledge of the cutter the blade projects. The retaining strip 16 ispreferably set back atboth sides relative to the cutting edges13a, 13bof the blade 13 (see FIG. 4) so that it is easy to reverse the blade 13.r

The retaining strip 16 receives the screw heads of the fixing screws 20in a recess. At least one corner of the retaining ledge cross-sectionremote from the cutting edge of the blades is chamfercd and/or radiused,so that a space 24 is formed in front of the chip cutting edge 13a or13b to receive the small pieces of wood cut off by the blades. Theretaining strip cross-section may be trapezoidal or have the shape of asection of a circle.

The chip cutting rotor 11 may be made as a frustoconical or cylindricalrotor. lts rotor arms 12 may be provided in the longitudinal extensionof the rotor, or have an inclined position.

The blade is usually made without cutting edge armour; it may, however,be provided with such an armour.

The blade 13 in accordance with the invention is made of a high qualitymaterial of low weight and can be discarded after having using andwearing both its cutting edges 13a, 13b successively. Replacement of theblade 13 is easy to carry out. Since there is only a relatively smalllength of blade projecting relative to the chip cutting blade holder,the cutting blade 13 can wear only to a slight extent corresponding tothe blade thickness, which in comparison with known embodiments leads toearly replacement of the cutting edges. This avoids the considerabledifferences in chip size produced in older machines by cutter wear.

I claim:

1. A chip cutting machine for producing wood chips, including a housing,a drum-shaped cutter cage fixed in said housing, cutter ribs in spacedrelationship provided around the circumference of said cage, a pluralityof cutters secured to said ribs, a chip cutting rotor rotating in saidcutter cage, a driving device for said rotor, rotor arms on said rotor,chip cutting blades on said rotor arms co-operating with said cutters ofsaid cutter cage, and a detachable fixing strip clamping each blade to asupporting surface on each rotor arm, said blades being of a thicknessbetween 1 and 5 mm, and having two cutting edges so as to be reversible.

2. A chip cutting machine as recited in claim 1, wherein said ribsextend diagonally to the axis of rotation of said rotor, said chipcutting blades tapering towards the ends with their cutting edgeslocated within the drum shaped cutter cage and being interchangeablymounted on said ribs, said blades being located on the generating lineof a conical frustum and coacting with the cutters of said cutter cagewhich is also frustoconical, each said cutter comprising a cutting bladeleading in the direction of rotation of said rotor and a rear stockblade in the direction of rotation of said rotor, said cutters beingmounted detachably at an angle relative to one another by means ofscrews on said ribs to define an adjustable chip passage gap leadingto-' wards a chip space defined between s tock blade and a cuttingblade.

3. A chip cutting machine as recited in claim 1, wherein said bladeshave their cutting edges located on the generating line of a cylinderand are adapted to cooperate with the cutters of a cylinder cutter cage,said cutters comprising a cutting blade leading in the direction ofrotation of said rotor and a rear stock blade in the direction of saidrotor, said cutters being detachably mounted at an angle relative to oneanother to define an adjustable chip passage gap leading towards a chipspace defined between a stock blade and a cutting blade.

4. A chip cutting machine as recited in claim 1, in which each cuttingblade is locationally fixed by screws and a retaining strip, and isclamped in a receiving space defined by said rotor arm, with only alength of blade equal to the blade thickness protruding.

5. A chip cutting machine as recited in claim 4, wherein said cuttingblades taper towards their ends and said retaining strips are similar inbasic shape to said cutting blades, but smaller in width to leave aportion of blade unclamped.

6. A chip cutting machine as recited in claim 4, wherein said retainingstrips are reversible and are bevstrip, each cutting blade and each ofsaid rotary arms, each screw having a partially cylindrical guide shaftpassing through said strip and blade, and a nut on each bolt on the sideof said rotor arm rearwards with re spect to the direction of rotationof said rotor.

1. A chip cutting machine for producing wood chips, including a housing,a drum-shaped cutter cage fixed in said housing, cutter ribs in spacedrelationship provided around the circumference of said cage, a pluralityof cutters secured to said ribs, a chip cutting rotor rotating in saidcutTer cage, a driving device for said rotor, rotor arms on said rotor,chip cutting blades on said rotor arms co-operating with said cutters ofsaid cutter cage, and a detachable fixing strip clamping each blade to asupporting surface on each rotor arm, said blades being of a thicknessbetween 1 and 5 mm, and having two cutting edges so as to be reversible.2. A chip cutting machine as recited in claim 1, wherein said ribsextend diagonally to the axis of rotation of said rotor, said chipcutting blades tapering towards the ends with their cutting edgeslocated within the drum shaped cutter cage and being interchangeablymounted on said ribs, said blades being located on the generating lineof a conical frustum and coacting with the cutters of said cutter cagewhich is also frusto-conical, each said cutter comprising a cuttingblade leading in the direction of rotation of said rotor and a rearstock blade in the direction of rotation of said rotor, said cuttersbeing mounted detachably at an angle relative to one another by means ofscrews on said ribs to define an adjustable chip passage gap leadingtowards a chip space defined between s tock blade and a cutting blade.3. A chip cutting machine as recited in claim 1, wherein said bladeshave their cutting edges located on the generating line of a cylinderand are adapted to co-operate with the cutters of a cylinder cuttercage, said cutters comprising a cutting blade leading in the directionof rotation of said rotor and a rear stock blade in the direction ofsaid rotor, said cutters being detachably mounted at an angle relativeto one another to define an adjustable chip passage gap leading towardsa chip space defined between a stock blade and a cutting blade.
 4. Achip cutting machine as recited in claim 1, in which each cutting bladeis locationally fixed by screws and a retaining strip, and is clamped ina receiving space defined by said rotor arm, with only a length of bladeequal to the blade thickness protruding.
 5. A chip cutting machine asrecited in claim 4, wherein said cutting blades taper towards their endsand said retaining strips are similar in basic shape to said cuttingblades, but smaller in width to leave a portion of blade unclamped.
 6. Achip cutting machine as recited in claim 4, wherein said retainingstrips are reversible and are bevelled at both longitudinal edgesrelative to the cutting edges of the associated blade, and radiusedalong one lateral longitudinal edge, each strip defining recesses forthe heads of said fixing screws.
 7. A chip cutting machine as recited inclaim 1, comprising a plurality of fixing screws for each retainingstrip, each cutting blade and each of said rotary arms, each screwhaving a partially cylindrical guide shaft passing through said stripand blade, and a nut on each bolt on the side of said rotor armrearwards with respect to the direction of rotation of said rotor.